Gwen lived in Meudon, near Paris, and at first kept a studio in Montparnasse. In the years between 1914 and 1925 she devoted her life to painting and religion. She sold pictures to her American patron John Quinn until his death in 1924, and exhibited and sold at the Paris Salons from 1919, but kept apart from the art world and lived alone. In private she developed a unique way of painting, producing different versions and repetitions of her one preferred subject. Nothing is known about most of her sitters.
Gwen travelled in France, often staying in villages in Brittany. Here she asked children to pose for rapid figure-studies in chalk and wash. She valued these drawings, and later displayed them in her own mounts and coloured folders.
A commission from the Convent in Meudon for a replica portrait of their founding mother led her to portray the nuns, and to make different versions of Mere Poussepin. She drew the orphans and nuns in church, adding watercolours in her studio. These paintings are profoundly meditative. They seem midway between portraiture and abstraction, the dry application of chalky colour as expressive as the impassive image.